Sanding machine



April 7, 1942. R. A. REID SANDING MACHINE Filed May 6, 1940 INVENTOR. 194 )WO/VD A R670 as ATZO/P/VEK Patented Apr. 7, 1942 UNITED STATES PATENT ogre 2,278,564 SANDING MACHINE Raymond A. Reid, Cedar Rapids, Iowa Application May 6, 1940, Serial No. 333,499

4 Claims.

This invention relates to sanding machines and has particular relation to means for holdin a sheet of abrasive, such as sandpaper, on the drum of a sanding machine.

In sanding machines of the character here considered, it is the usual practice to employ a revolving drum or belt to which a strip of abrasive, such as sandpaper or emery paper, is secured. In ordinary practice, such abrasive strips are generally secured tothe drum or belt by clamping the abrasive strip to the drum, but the means ordinarily used have a disadvantage in that the paper loosens in use, and is destroyed, by reason of looseness or slackness, in a relatively short period. I have found that this loosencss occurs from two possible causes; improper applicationand stretching of the paper from expansion due to heat, and the stress of operation.

It is a generalobject of my invention to over-t come this disadvantage of the usual clamping means, and to provide a spring member for tightening the sandpaper strip by spring pressure while the sanding machine is in use.

Another general object of the invention is th provision of means such as will prevent incorrect application of paper.

I have found that it is advisable, in using a spring tightener, to' employ a latch for holding the spring tightener in cocked or stressed condition while the sandpaper strip is being clamped to the tightener, but I have also found that users frequently forget or neglect to release the latch on the tightener', so that the spring may tighten the sandpaper strip in use, thus, of course, nullifying the effect of the spring.

This condition, then, leads to another object of' my invention, which is to provide means which will automatically release the latch to permit the spring to become effective as soon as the machine has started up.

Other and further features and objects of the invention will be more apparent. to those skilled in the art upon a consideration of the accompanying drawing and following specifications, wherein is disclosed a single exemplary embodiment of the invention, with the understanding,

cut joint.

Figure 3 is a fragmentary view in end elevation of the tightening means shown in Figure 2 as it appears when the latch has been released, either by centrifugal force or'manual operation thereof.

Figure 4 is a partial view in section, taken along the line 44 of Figure 2, and illustrating the sanding strip tightening means, and

Figure 5 is a partial or fragmentary view of the clamping means employed for clamping the opposite end of the sanding strip to the drum.

Referring now to the'drawing:

' The device illustrated in Figure 1 consists of a sander casing ill in which a sander drum H is rotatably mounted. The casing has a bi ting handle l2, and the energization of the sanding machine is controlled by means of the switch 13. A removable front llia is provided on the sander casing. The machine is moved and guided by means of the handle M, and a bag i6 is provided for the dust from the sanding operation. The member I1 is a smallmotor used to power a blower for carrying the dust from the sender into the bag IS.

The drum ll, illustrated more particularly in Figure 1, consists of a cylindrical member having the hub, such as I la, the fan spokes l lb, and the drum proper illustrated at H0. The drum He is covered on its outer face with a tightly wound strip of fabric, illustrated at l8, on which a cylindrical rubber pad I!) is secured.

The sandpaper strip, illustrated at 2|, is formed of a paper or cloth strip to which abrasive, such as sand or emery, has been applied. The strip 2i is cut on the bias at its ends so that, when the strip is applied to a cylinder, the ends abut one another and the biased edges adjoin, so that when the sanding drum is applied to a work surface, contact of the sandpaper strip with the work surface is transferred, when the drum is rotating, from the end of the strip to the beginning of the strip withoutthe use of a square In this way tearing of the joint at the ends of the strip is avoided.

The ends of the strip 2!, therefore, are narrow triangular pieces, such as illustrated at Zia and Mb. The drum preferably revolves in the direction of the arrow, and the end 2|b of the stripZl, which may be termed the Heading end, is clamped to the sanding drum by means of a'conventional clamp comprised of the abutment 22, the clamping clip 23, and a screw 24. as illustrated in Figure 5.

The spring tightening means, constructed according to one embodiment of my invention, is preferably engaged to what may be termed the "trailing end 21a of the strip 2 I.

The spring tightening means is received with in a recess between the hub and the cylinder of the drum and is disposed between the fan cylinder I l.

blade spokes of the drum. The tightener, constructed according to my invention, includes a disc-like member 26 rotatably mounted by means of a screw 21 on a plate-like portion 23 of the A curved arm or latch 29 is pivotally attached to the disc near its periphery by means of a screw 3|. The latch arm 29 has a curved weight portion 29a and a hooked outer end 29b. A strap or plate-like strip 33 .s secured to a spoke Nb and against the hub of the cylinder by means. of a cap screw 34, and a free end of this strip is bent radially to the hub to form- The latch arm 29 is preferably so located that when the spring tightening means is rotated to the "cocked position, as hereinafter described, the latch falls by gravity into engagement with the hooked portion 330 of the strap member 33. A hump or raised portion 29b is preferably provided on the latch arm 29 to ride on the lip or flange l'le during the first portion of the travel to cocked position of the latch to prevent the hooked end thereof from striking or becoming fouled on spokes llb or hub Ila or, in fact, on any part of the machine.

A coiled torsion spring 36 is located within the chamber 35 formed by the inwardly turned edge 25a of the disc 26, and this coiled spring 36 is secured at its inner end to the boss 28a, which is a part of the flangeor plate-like member 28, and at its outer end to the flange 26a of the disc 26. The spring is so coiled and flexed that rotation of the disc 26 in a counter-clockwise direction is induced when the latch 29b is released from the hook 33a. It is this spring 36 which tightens the sandpaper strip 2| on the drum. The end of the sandpaper strip 2| is secured to the disc by means of a U-shaped boss 31, a clamping strap 38, and screw 39, the screw 39 serving to clamp the strap 38 against one arm of the boss 31, and to thus engage the sandpaper strip against the other arm of the U-shaped boss.

A helical spring 41!, received on the screw 39 between the boss 31 and the clamping strap 38, facilitates the insertion of the end of a sanding strip into the clamp.

It will be noted that the clamping strap 38 is bent or hooked on one end, as shown at 38a. This bent portion of the clamp is adapted to come to rest against the shoulder Ild of the sanding drum No if the latch member 28 is out of engagement and if there is no sanding strip in place, or if the sanding strip breaks.

In use, the spring tightening means is rotated until it is in the latched position shown in Figure 2. The trailing tip 2la of the sanding strip 2| is secured to the spring tightening means by means of the clamping means 31, 3B and 39. If the operator then releases the latch 29b from the hook 33a, the disc 25 will rotate because of the biasing eifect of the helical spring 36 to tighten the sandpaper strip 2| on the drum ll. If, however, as is frequently thecase, the operator does not understand or forgets that the latch 29 must be released, and starts up the machine, the weight 29a will be biased outwardly or radially by centrifugal force as the drum picks up speed. Before top speed is reached, the

centrifugal force will cause the latch 29b to be disengaged from the hook 33a' to thus release the disc to permit it to function in tightening the strip 2|.

It is apparent, then, that by means of my invention, the operator may secure a sandpaper strip to the drum of a sander or the like without having to manually hold the securing device against the force of the self tightening spring, and that release of the self tightening device, to permit it to function, is automatic on starting the sander and is operable whether or not it is released by the operator.

The position of the stretching device, when in loaded position, makes it impossible to secure the sanding paper on the drum unless the device is in cocked position.

Although I have described a specific embodiment of my invention, it is apparent thatmodiflcations thereof may be made by those skilled in the art. Such modifications may be made without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

1. In a device of the character described including a drum and a sanding strip, spring means for tightening the sanding strip on the drum, a latch means for holding the tightening means in stressed condition while the sanding strip is applied, and weighted means operable by centrifugal force to release the latch means as soon as the drum is rotated at a speed approaching normal operating speed.

2. In a sanding machine including a sanding drum, a take-up member pivotally attached to the sanding drum, spring means connected therewith, a clamping means for clamping a sandpaper strip to the take-up member, a latch mem her for holding the spring means in stressed condition, and a weight co-operatively mounted with the latch means to throw. the latch means out of engagement by centrifugal force when the drum is rotated.

3. A sandpaper clamping and tightening means for use on a sanding drum, comprising a disclike member, means for rotatably mounting said member near the end of the sanding drum, a torsion spring mounted between the disc-like member and the drum, means for clamping a sanding strip to the disc-like member near the periphery thereof, means for latching the disc in inoperative position, and means for releasing the latching'means.

4. In a sanding machine including a rotatable drum, means for securing a sanding strip to the periphery of the drum, said means including a pivotally mounted clamp for gripping one end of the strip, spring means for biasing the clamp in one direction to tighten the strip, latch means for holding the clamp in inoperative position against the action of the spring, whereby the strip may be tightened on the sanding drum by releasing the latch after the end of the strip has been secured by the clamp, and a weighted member, comprising part of the latch means, so disposed as to be actuated by centrifugal force during rotation of the drum to fly outwardly and disengage the latch if the latch has not already been disengaged manually.

RAYMOND A. REID. 

